Fundamentals of heterocyclic chemistry importance in nature and in the synthesis of pharmaceuticals

FUNDAMENTALS OF HETEROCYCLIC CHEMISTRY FUNDAMENTALS OF HETEROCYCLIC CHEMISTRY Importance in Nature and in the Synthesis of Pharmaceuticals LOUIS D QUIN Adjunct Professor, University of North Carolina Wilmington James B Duke Professor Emeritus, Duke University Professor Emeritus, The University of Massachusetts JOHN A TYRELL, PH.D University of North Carolina Wilmington A JOHN WILEY & SONS, INC., PUBLICATION Copyright  2010 by John Wiley & Sons, Inc All rights reserved Published by John Wiley & Sons, Inc., Hoboken, New Jersey Published simultaneously in Canada No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance 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loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages For general information on our other products and services or for technical support, please contact our Customer Care Department within the United States at (800) 762-2974, outside the United States at (317) 572-3993 or fax (317) 572-4002 Wiley also publishes its books in a variety of electronic formats Some content that appears in print may not be available in electronic formats For more information about Wiley products, visit our web site at www.wiley.com Library of Congress Cataloging-in-Publication Data: Quin, Louis D., 1928– Fundamentals of heterocyclic chemistry : importance in nature and in the synthesis of pharmaceuticals / Louis D Quin, John A Tyrell p cm ISBN 978-0-470-56669-5 (cloth) Heterocyclic chemistry Heterocyclic compounds— Synthesis I Tyrell, John A II Title QD400.Q46 2010 547 59–dc22 2009051019 Printed in Singapore 10 ă To our wives, Gyongyi Szakal Quin and Ann Marie Tyrell, with deep appreciation for their understanding and support during the preparation of this book CONTENTS PREFACE xiii ACKNOWLEDGMENT xv Chapter THE SCOPE OF THE FIELD OF HETEROCYCLIC CHEMISTRY References / Appendix / Chapter COMMON RING SYSTEMS AND THE NAMING OF HETEROCYCLIC COMPOUNDS 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 General / Naming Simple Monocyclic Compounds / 11 Handling the “Extra Hydrogen” / 13 Substituted Monocyclic Compounds / 14 Rings With More Than One Heteroatom / 15 Bicyclic Compounds / 17 Multicyclic Systems / 19 The Replacement Nomenclature System / 21 Saturated Bridged Ring Systems / 22 vii viii CONTENTS References / 23 Review Exercises / 23 Chapter NATURE AS A SOURCE OF HETEROCYCLIC COMPOUNDS 29 3.1 General / 29 3.2 Naturally Occurring Nitrogen Heterocyclic Compounds / 30 3.3 Oxygen Compounds / 51 3.4 Sulfur and Phosphorus Heterocyclic Compounds in Nature / 55 References / 57 Chapter PRINCIPLES OF SYNTHESIS OF AROMATIC HETEROCYCLES BY INTRAMOLECULAR CYCLIZATION 58 4.1 General / 58 4.2 Some of the Classic Synthetic Methods / 60 4.3 Cyclizations Involving Metallic Complexes as Catalysts / 78 4.4 Cyclizations with Radical Intermediates / 82 4.5 Cyclizations by Intramolecular Wittig Reactions / 84 4.6 Synthesis of Heterocycles by the Alkene Metathesis Reaction / 89 References / 91 Review Exercises / 92 Chapter SYNTHESIS OF HETEROCYCLIC SYSTEMS BY CYCLOADDITION REACTIONS 5.1 The Diels–Alder Reaction / 98 5.2 Dipolar Cycloadditions / 112 5.3 [2 + 2] Cycloadditions / 122 References / 125 Review Exercises / 126 98 313 HETEROCYCLIC AGROCHEMICALS 11.1.3.1 Triazolopyrimidines Flumetsulam was the first of a new family of herbicides containing the triazolo[5,1-a]pyrimidine ring system.2 Important in this compound also was the presence of a sulfonamido group Research has continued in the triazolopyrimidine area; a report published in 20093 describes structure–activity relations in this family and the course of research that led to the discovery of the new highly valuable herbicide penoxsulam.3 Here, the ring system has [1,5-c] fusion and the reversed structure of the sulfonamide group It is active against grass and broadleaf weeds Triazolopyrimidines exhibit their herbicidal activity by inhibiting the enzyme acetolactate synthase F2CH F OMe O N N N N N SO2NH NHSO2 N F N Me N CF3 flumetsulam OMe penoxsulam 11.1.3.2 Pinoxaden This herbicide is active against grass weed species in the growing of grain cereal crops, especially rice It is an inhibitor of acetylcoenzyme A carboxylase Its structure evolved from considerations of the pyrazolidine-3,5-diones (and their enol derivatives), many of which have valuable herbicidal activity (e.g., structure 11.4, designated CGA 271312 by Ciba-Geigy) The development of pinoxaden is described in a recent review article.4 Me Et O O N N O Me Me N N Me O Et O C(O)Bu-t 11.4 pinoxaden The key step in the construction of the pyrazolo[1,2-d]-1, 4, 5oxadiazepane ring is shown in Scheme 11.5 314 SYNTHETIC HETEROCYCLIC COMPOUNDS IN AGRICULTURAL Et O Et COOEt N HN + Me O O Me N HN COOEt Et Et O Scheme 11.5 11.1.3.3 Alkyne-Containing Heterocycles Many heterocycles with alkyne groups have potent pesticidal activity and constitute another broad family receiving attention As herbicides, they serve as inhibitors of the enzyme protoporphyrinogen-IX oxidase, which catalyzes the last step in the biosynthesis of chlorophyll A typical herbicidal heterocycle under development is pyraclonil, which is shown along with several other useful alkynyl-heterocycles in a review published in 2009.5 This compound, unique with its two pyrazole rings, is useful in control of broadleaf weeds and grass in rice fields Another unique compound, which is based on the isoindole system, has structure 11.5 NC NMeCH2C N CH F H2C Cl N N N C Cl H2 C F N O HC O pyraclonil 11.5 11.1.3.4 Thiamethoxam This new insecticide is classed as a member of the important neonicotinoid family, which act as agonists of the nicotinic acetylcholine receptor Thiamethoxam has systemic activity, meaning that a level of it or active metabolic products6 is maintained in the plant and ingested by the attacking insects It is especially used in the protection of tomato crops NO2 N S Cl N N N O thiamethoxam Me 315 HETEROCYCLIC AGROCHEMICALS 11.1.3.5 Chlorantraniliprole Diamide insecticides are another class of recently introduced crop protection agents, which behave as activators of ryanodine receptors in the insect This leads to uncontrolled calcium release in muscles Chlorantraniliprole is a member of this family7 and is in commercial use for protection from various pests Br Me O H N N C N Cl C O Cl N NHMe chlorantraniliprole 11.1.3.6 Triketones with Heterocyclic Substituents Triketones represent a well-studied, but still developing, family of herbicides Some with pyridyl substituents are among the most active Much of the research in this area has been reviewed.8 The triketones are inhibitors of the plant enzyme 4-hydroxyphenylpyruvate dioxygenase (HPPD), which plays a key role in the biosynthesis of plastoquinone and tocopherol Compound 11.6, which is known as nicotinoyl syncarpic acid, is shown as a typical structure of this type Its potent herbicidal activity led to synthetic work that has yielded many related structures in an effort to improve selectivity in the herbicidal action O O Me C Me O Me O Me N CF3 Me 11.6, nicotinoyl syncarpic acid 11.1.3.7 Fipronil This insecticide, which is a pyrazole derivative, is an effective agent for the elimination of various pests, such as wasps, bees, cockroaches, fleas, etc It acts by disrupting the central nervous system of the insects, specifically by blocking chloride ion passage in the system It is another discovery of the biological effectiveness of fluorine-containing substituents on a heterocyclic ring 316 SYNTHETIC HETEROCYCLIC COMPOUNDS IN AGRICULTURAL NC Cl N CF3 N F3C S O Cl NH2 fipronil 11.2 APPLICATIONS OF HETEROCYCLIC COMPOUNDS IN COMMERCIAL FIELDS Heterocyclic compounds are of great importance in many different fields of commerce They represent specialized, well-developed areas of technology, and only a brief comment on such areas can be provided here Much more detailed presentations are given in Comprehensive Heterocyclic Chemistry1 and in the text Heterocycles in Life and Society.9 An extremely important application of heterocyclic compounds is in the field of dyes and pigments Extended conjugation is an important ingredient for a compound to be colored, and heterocyclic systems, usually multicyclic, in great numbers have been constructed around this principle The field is enormous, as is demonstrated in the review by D R Waring in Comprehensive Heterocyclic Chemistry.1b Industrial organic chemistry can trace its beginnings back to the (accidental) discovery of mauveine (11.7) in 1856 by W H Perkin; it was the first organic compound to be prepared synthetically at the industrial scale Another heterocyclic compound, indigo (11.8), was derived from natural sources and was used for centuries before it was synthesized in 1883 and later made commercially These two early compounds display the extended conjugation so important in the development of new dye and pigment chemicals Me N Me PhHN N NH2 H N O 11.7, mauveine O N H 11.8, indigo APPLICATIONS OF HETEROCYCLIC COMPOUNDS IN COMMERCIAL FIELDS 317 Many types of dyes are available, which require the presence of the proper functional groups to cause adherence to fabrics and other materials, and many techniques for the dying process are in use today Technology in the area of photography is highly developed, making use of heterocyclic compounds in various ways in the several steps of the process Discussions will be found in Comprehensive Heterocyclic Chemistry.1c,d Heterocyclic compounds can participate in polymer technology in several ways They can be pendants on a polymer chain, as might be formed from the polymerization of vinyl monomers with heterocyclic substituents There are processes where the polymer is formed by closing heterocyclic rings Finally, heterocyclic groups can be added to previously formed polymers These processes are described by S M Heilmann and J K Rasmussen in Comprehensive Heterocyclic Chemistry.1e Hindered heterocyclic amines are used as light stabilizers in plastic and coating formulations, protecting against degradation by ultraviolet radiation These agents are known as hindered amine light stabilizers (HALSs) and are commonly derivatives of 2,2,6,6-tetramethylpiperidine.10 An example of a HALS agent is Tinuvin 770 (BASF), which is a diester of sebacic acid and 4-hydroxy-2,2,6,6-tetramethylpiperidine It is thought to act through the formation of a piperidinoxyl radical.11 O O O Me Me N H C (CH2)8 Me Me Me Me C O Me N H Me tinuvin 770 A thriving and highly important field is the construction of coordination complexes from metallic species and heterocycles These complexes can be useful as reaction catalysts and have other uses as well To illustrate the catalyst area (which is large), the zirconium complex formed from the anion of indenylindoyl anion (11.9), and ZrCl4 is offered as an example The complex has the formula Zr(11.9)2 Cl2 and is an excellent catalyst for the polymerization of olefins.12 318 SYNTHETIC HETEROCYCLIC COMPOUNDS IN AGRICULTURAL Me N Me C H 11.9 Also, we have noted in Chapter 10 that heterocycles with chirality can form complexes that are useful catalysts for asymmetric synthesis This is a field of great contemporary interest Another valuable property is the selective binding of certain metallic species.13 An example of this type of ligand is the 1,10phenanthroline derivative 11.10 (PDALC), which selectively binds to larger metallic cations such as Ca++ and Pb++ The crystallized coordination complex formed from calcium perchlorate has the formula [Ca(PDALC)2 ](ClO4 )2 · H2 O Certain heterocyclic ligands have special value in selective complexation because, as in the case of PDALC, the backbone containing the ligating nitrogen atoms can be rigid and offer a cavity of fixed geometry to receive the metal N N H2C CH2 OH HO 11.10 A relatively new and still developing field is the use of heterocyclic compounds in electro-optical applications, which includes light-emitting diodes (LEDs), thin-film transistors, and photovoltaic cells To possess these properties, molecules must have extended conjugated unsaturation This lowers the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gap and causes light absorption at long wavelengths One type of useful structure has several heterocyclic rings such as pyrrole or thiophene joined in a linear fashion The phosphole ring system is a new participant in this type of array This is illustrated by compound 11.11, in which two thiophene rings are attached to a central phosphole ring (as the sulfide) 319 REFERENCES S P Ph S S 11.11 This compound has LED properties; when deposited as a thin film between a bilayer cathode and anode, yellow light was emitted by application of a low voltage.14 Other related structures are being examined for similar electro-optical activity Another new application of heterocyclic compounds is in the field of ionic liquids These compounds generally are quaternary salts of certain heterocyclic bases, and they are finding use as high-boiling polar solvents for extractions or as reaction media.15 Common among the ionic liquids known so far are salts of imidazole, which are shown as follows Me N N R X REFERENCES (1) A R Katritzky and C W Rees, Eds., Comprehensive Heterocyclic Chemistry, Vol 1, Pergamon, Oxford, UK, 1984; (a) P J Crowley, Chapter 1.07; (b) D R Waring, Chapter 1.12; (c) J Bailey and B A Clark, Chapter 1.14; (d) J Stevens, Chapter 1.13; (e) S M Heilmann and J K Rasmussen, Chapter 1.11 (2) W A Kleschick, B C Gerwick, C M Carson, W T Monte, and S W J Snider, J Agric Food Chem., 40, 1083 (1992) (3) T C Johnson, T P Martin, R K Mann, and M A Pobanz, Bioorg Med Chem., 17, 4230 (2009) (4) M Muehlebach, M Boeger, F Cederbaum, D Cornes, A A Friedmann, J Glock, T Niderman, A Stoller, and T Wagner, Bioorg Med Chem., 17, 4241 (2009) (5) C Lamberth, Bioorg Med Chem., 17, 4047 (2009) (6) R Karmakar, R Bhattacharya, and G Kulshrestha, J Agric Food Chem., 57, 6360 (2009) 320 SYNTHETIC HETEROCYCLIC COMPOUNDS IN AGRICULTURAL (7) G P Lahm, D Cordova, and J D Barry, Bioorg Med Chem., 17, 4127 (2009) (8) R Beaudegnies, A J F Edmunds, T E M Fraser, R G Hall, T R Hawkes, G Mitchell, J Schaetzer, S Wendeborn, and J Wibley, Bioorg Med Chem., 17, 4134 (2009) (9) A F Pozharskii, A T Soldatenkov, and A R Katritzky, Heterocycles in Life and Society: An Introduction to Heterocyclic Chemistry and Biochemistry and the Role of Heterocycles in Science, Technology, Medicine and Agriculture, Wiley, New York, 1997 (10) H Jia, H Wang, and W Chen, Radiation Phys Chem., B76, 1179 (2007) (11) C Saron, M I Felisberti, F Zulli, and M Giordano, J Braz Chem Soc., 18, 900 (2007) (12) S Nagy, B P Etherton, R Krishnamurti, and J A Tyrell, U.S Patent 6,376,629 (April 23, 2002) (13) R T Gephart III, N J Williams, J H Reibenspies, A S De Dousa, and R D Hancock, Inorg Chem., 47, 10342 (2008) (14) C Fave, T.-Y Cho, M Hissler, C W Chen, T.-Y Luh, C.-C Wu, and R R´eau, J Am Chem Soc., 125, 9254 (2003) (15) R P Singh, R D Verma, D T Meshri, and J M Shreeve, Angew Chem Int Ed , 45, 3584 (2006) APPENDIX UNIFIED AROMATICITY INDICES (IA ) OF BIRD [Taken from C W Bird, Tetrahedron, 48, 335 (1992)] Compound IA Compound 1,3-Oxazole 1,2,4-Oxadiazole 1,2-Oxazole Furan 1,2,5-Oxadiazole Tellurophene 1,3,4-Oxadiazole 1,2,3-Thiadiazole Selenophene 1,2,3-Triazine Imidazole Thiazole Pyridazine 1,3,4-Thiadiazole Thiophene 47 48 52 53 53 59 62 67 73 77 79 79 79 80 81.5 Pyrimidine Pyrrole Pyridine 1,2,4-Triazine 1,2,4-Thiadiazole 1H-Tetrazole Pyrazine Pyrazole 1H-1,2,3-Triazole 1,2-Thiazole 1,2,4,5-Tetrazine Benzene 1,3,5-Triazine 1H-1,2,4-Triazole Pentazole IA 79 85 86 86 89 89 89 90 90 9l 98 100 100 100 109 Fundamentals of Heterocyclic Chemistry: Importance in Nature and in the Synthesis of Pharmaceuticals, By Louis D Quin and John A Tyrell Copyright  2010 John Wiley & Sons, Inc 321 INDEX Acetazolamide, 241–242 ACIPHEX, 204 Acrivastine, 249 Adenine, 48, 258, 265 Adenosine, 47 Alkaloids biosynthesis of, 33–36 erythrina family of, 42–43 indole family of, 41–42 isoquinoline family of, 39–40 marine, 43–44 piperidine family of, 37–38 pyridine family of, 38–39 pyrrolidine family of, 36–37 quinoline family of, 40–41 Alkene metathesis, 89 Grubbs’ catalyst in, 89 in formation of heterocycles, 90–91 6-Aminopenicillanic acid, 233 Annulenes, 156–157 Aromaticity of benzene, 132–135 of pyridine, 138–140 of pyrimidines, 155 of pyrrole, 170–175 Ascorbic acid, 51–52 Atropine, 37 AVANDIA, 205 Aza[10]annulene, 158 Aza[14]annulene, 158 Aza[18]annulene, 157 Azacyclobutadiene, 158 Aza-Wittig reactions, 86–87 diazepin-2-ones from, 88 isoquinolines from, 88 1,3-oxazoles from, 88 pyrroles from, 87 pyrrolidines from, 87 quinazolinones from, 88 Azepines, 211–213 Azetidines, conformation of, 290–291 Azetidinones, 123–125, 231 Aziridines barrier to pyramidal inversion in, 285 geometry of, 284 ring opening of, 283–284 synthesis from 1,2,3-triazolines of, 286 Azonines, proton NMR spectra of, 187 Azomycin, 235–236 Fundamentals of Heterocyclic Chemistry: Importance in Nature and in the Synthesis of Pharmaceuticals, By Louis D Quin and John A Tyrell Copyright  2010 John Wiley & Sons, Inc 323 324 Azumolene, 234 Baldwin’s Rules for ring closure, 287–290 Bamiphylline, 267 Barbituric acid, 199, 258, 263 Benzodiazepines, 211–212, 254–256 Beta-lactams (see Azetidinones) Bird index of aromaticity, 172 Bird unified index of aromaticity, 172 Bischler-Napieralski isoquinoline synthesis, 68–69 Caffeine synthesis, 266 cAMP, 56 Carbazoles, 79–80 Cetirizne (+, −) form (ZYRTEC), 300–301 (−)-enantiomer (XYZAL), 300–301 CHANTIX, 212 Chloroquine, 201, 209 Chlorantraniliprole, 315 Chroman, 53 CIALIS, 207 Ciprofloxacin, 209–210, 252–253 Cocaine, 37 Combes quinoline synthesis, 67 Coumarin, 54 [2 + 2] Cycloadditions azetidinones from, 123 beta-lactams (see azetidinones) Cytosine, 258, 262 Decitabine, 269 Diazepam, 255–256 Diazepin-2-ones, from aza-Wittig reagents, 88 Diels-Alder reaction, 98–9 intramolecular, 109–110 mechanism of, 99–103 in the synthesis of heterocycles, 99–109 Dilantin, 237 Dimetridazole, 236–237 1,3-Dioxanes, conformation of, 293 1,2,3-Dioxazoles Dipolar cycloadditions, 112–122 with azides, 114–115 with diazoalkenes, 114 1,2,3-dioxazoles from, 119 isoxazoles from, 116–117 mechanism of, 120–122 with nitrile oxides, 114, 118 with nitrones, 113–115 1,2,4-oxadiazoles from, 119 tetrahydrofurans from, 118 INDEX 1,2,3,4-tetrazoles from, 119 1,2,3-triazoles from, 115 DNA, 259 (S)-Escitalopram, 301 Ethionamide, 248 Ethylene oxide reactions of, 283 synthesis of, 286 Fadrozole, 239 Famotine, 254 Feist-Benary furan synthesis, 76–77 Fipronil, 315–316 Fischer indole synthesis, 242–244 Flumazenil, 270–271 Furans addition reations of, 182–183 Diels-Alder cycloadditions with, 183 electrophilic substitutions of, 182, 226 in the synthesis of ZANTAC, 226–227 synthesis of, 62, 76, 77, 225 as dienes in the Diels-Alder reaction, 108 GLEEVEC, 205, 215 Guanine, 258 Heck metal-catalyzed ring closures, 78–80 Histamine, 51 Histidine, 51 Hofman Exhaustive Methylation, 32–35 Hydantoin, 237 Hydrochlorothiazide, 203 Hydrogen bonding of pyrimidine bases to purine bases, 259 to guanine, 165 Imatinib, 205 Imidazole aromaticity of, 188, 235 2-nitro, 235 salts as ionic liquids, 319 tautomerism of, 187, 236 Imidazo[1,5-a]pyridine, 238 IMITREX, 207 Indigo, 316 Indoles Bischler synthesis of, 244 electrophilic substitutions of, 185–186 Fischer synthesis of, 242–246 Madelung synthesis of, 244–245 pharmaceuticals, 207–208 325 INDEX Indomethacin, 245 Indolizidines, conformation of, 295 Isoquinolines from aza-Wittig reagents, 88 Bischler-Napieralski synthesis of, 253–255 Isoxazoles, 116–118, 233–234 Lavoltidine, 240 (S)-Lercanidipine, 301 LIBRIUM, 211 Light-emitting diodes, heterocyclic, 318–319 Losartan, 240–241 LUNESTA, 205 Lysergic acid, 42 Mauveine, 200, 316 Medazepam, 255 Memotine, 254 Mesoionic compounds, 189–191 Methopromazine, 270 Methotrexate, 214–215 Minoxidil, 263 Monobactam antibiotics, 231 Morphine, 40, 198 Munchnones, 191 NEXIUM, 204 Niacin, 49, 205 Nicotine, 31 Nicotinic acid, 34, 38 NICS (see Nucleus Independent Chemical Shift) Nifedipine, 247–248 Nomenclature of bicyclic heterocycles, 17–19 Hantzsch-Widman system of, 10–21 of monocyclic heterocycles, 11–17 of multicyclic heterocycles, 19–21 replacement system of, 21–22 saturated bridged heterocycles, 22–23 Nuclear Magnetic Resonance (NMR) applications proton, 136, 140–141, 160, 174–175, 184, 187 carbon-13, 135–136, 141–143, 282, 296 nitrogen-14 and -15, 143 Nucleoside synthesis, 264–265 Nucleus Independent Chemical Shift of furan, 174 of pyrrole, 174 of thiophene, 174 Ofornine, 248–249 Omeprazole, 204 Opium, 198 Oxacillin, 233 1,2,3-Oxadiazoles, 189–190 1,2,4-Oxadiazoles, 119 7-Oxanorbornenes, 108 1-Oxa-3-azacyclohexanes, conformation of, 297–298 1,2-Oxazine, synthesis by Diels-Alder cycloaddition, 107 1,3-Oxazoles, from aza-Wittig reagents, 88 Oxiranes (see also ethylene oxide) chiral derivatives from Sharpless epoxidation, 286 syntheses of, 286 Paal-Knorr synthesis of furans, 62 of 1,3-oxazoles, 234 of pyrroles, 60–61 of 1,3-thiazoles, 63 of thiophenes, 62 Papaverine, 34–35, 39 Pauson-Khand ring closures, 81 Penicillin 49–50, 231 Pesticides with 5-membered rings, 311–312 pinoxaden synthesis, 313–314 pyraclonil, 314 pyridine derivatives, 307–308 pyrimidine derivatives, 308–310 thiamethoxam, 314 triazine derivatives, 310–311 triazolopyrimidine, 313 Phenanthrolines, 318 Phenobarbital, 199 Phenothiazines, synthesis of, 270 Phosphetane, geometrical isomers of, 292 Phosphinines NMR of, 162 synthesis of, 162 1,3,5-triphenyl, 161–162 Phospholanes, geometrical isomers of, 292 Phospholenes, synthesis of, 111 Phospholes aromaticity in, 184–185 Friedel-Crafts acylation of, 185 proton NMR spectra of, 184 Phosphorinanes (phosphinanes) conformation of, 295–296 geometrical isomers of, 295 synthesis of, from cycloaddition, 109 326 Piperidines, 37–38 conformation of, 293–294, 296–297 Piperine, 31–32, 38 Porphyrins, 44–46 delocalization in, 159 tautomerism in, 15 PREVACID, 204 Prifelone, 228 PRILOSEC, 204 Prinomide, 224 Prontosil, 201–202 PROTONIX, 204 Pteridines, synthesis of, 266 Purines, 46 delocalization in, 189 synthesis of, 266–267 tautomerism in, 189, 265 Traube synthesis of, 266–267 Pyraclonil, 314 Pyrans, synthesis of, by Diels-Alder cycloaddition, 107–108 Pyrazoles, 239 Pyridazines, synthesis of, by Diels-Alder cycloaddition, 106 Pyridines aromaticity of, 138–140 basicity of, 144–145 electrophilic substitution of, 147–150 geometry of, 140 Hantzsch synthesis of, 246–248 NMR properties of, 140–143 N-oxides from, 146, 153–154 nucleophilic substitution of, 150–153 pesticides, table of, 307–308 pharmaceuticals, 204–206 quaternization of, 145–146 reduction of, 146 syntheses of, 248–249 synthesis by Diels-Alder cycloaddition, 104–106 tautomerism of hydroxy derivatives, 151–152, 162–164 Pyrazines, synthesis of, 63–65 Pyridones, 151–152, 162–164 Pyrimidines, 46 aromaticity of, 155 basicity of, 256 electrophilic substitution of, 257 hydrogen bonding in, 258–259 N-oxides of, 259 pesticides, table of, 308–310 pharmaceuticals, 213–217 synthesis of, 65–66, 70–73, 260–264 INDEX tautomerism in, 165, 257–258 Pyrimidones, 257–263 Pyrrolam A, 90 Pyrrole acetylation of, 176 acidity of, 179–180 aromaticity of, 170–175 from aza-Wittig reagents, 87 basicity of, 179–180 coupling with diazonium ions, 178 Diels-Alder reaction with, 181 electrophilic substitutions of, 175–176 Hantzsch synthesis of, 223 Knorr Synthesis of, 75–76 metallation of, 181 nitration of, 176 Paal-Knorr synthesis of, 60–61, 223 reaction of, with carbonyl compounds, 178 syntheses of, 222–225 Vilsmeier-Haack formylation of, 177 Pyrrolidines conformation of, 291–292 from aza-Wittig reagents, 87 Pyrylium ions, 160–161 Quinazolinones, from aza-Wittig reagents, 88 Quinine, 40–41, 200 Quinolines Conrad-Limpach synthesis of, 250252 Friedlăander synthesis of, 251252 pharmaceuticals, 209210 Skraup synthesis of, 250 Quinolizidine, conformation of, 295 Quinolones, 209–210, 250–252 Radicals in ring closures, 82–84 RNA, 259 Romazarit, 233–234 SEROQUEL, 212 Serotonin, 207 SINGULAIR, 209 Strychnine, 42 Sulfa drugs, 202 Sulfathiazole, 229–230 Sulfolanes, synthesis of, 111 Sulfonamides, 202–204 Sumatriptan, 207, 246 Sydnone delocalization in, 190 as a 1,3-dipole in cycloaddition, 190 synthesis of, 189 1,2,3,4-Tetrazoles, 119, 240–241 327 INDEX Tetrabromopyrrole, 177 Tepoxalin, 239 Tetrahyydropyrans, conformation of, 293 Teroxirone, 269 Thalidomide differing biological activity of (R) and (S) enantiomers, 299 teratogenic action of (R,S) mixture, 299 1,3,4-Thiadiazoles, 241–242 Thiamethoxam, 314 Thiamine, 49 Thianes, conformation of, 296 Thiazoles aromaticity of, 188 Hantzsch synthesis of, 229–231 synthesis of 2-amino derivatives, 229–230 Thiophenes electrophilic substitutions of, 183–184 Hinsberg synthesis of, 227 synthesis using a Wittig reaction, 227–228 Paal-Knorr syntheses of, 62, 227 Thiopyran, synthesis of, by cycloaddition, 109 Thymine, 258, 261 Tinuvin 770, 317 Traube purine synthesis, 72–73, 266–267 1,3,5-Triazines N-alkylation of cyanuric acid, 269 pesticides, table of, 310–311 synthesis of, from cyanamide, 268 synthesis of, from cyanogen chloride, 268 synthesis of, from 1,3,5-triazapentane derivatives, 269 synthesis of trichloro- (cyanuric chloride), 268 synthesis of triketo- (cyanuric acid), 268 1,2,3-Triazoles, 115, 116, 188 1,2,4-Triazoles, 188, 239–240 Trăogers base, 294 Trimethoprim, 264 Tryptophan, 34, 41, 51 Uracil, 258, 261 VALIUM, 211 VIAGRA, 214 Vitamin B3 , 205 Wittig reaction, 84–85 XANAX, 211 ZANTAC, 226 ... FUNDAMENTALS OF HETEROCYCLIC CHEMISTRY FUNDAMENTALS OF HETEROCYCLIC CHEMISTRY Importance in Nature and in the Synthesis of Pharmaceuticals LOUIS D QUIN Adjunct Professor, University of North... Fundamentals of Heterocyclic Chemistry: Importance in Nature and in the Synthesis of Pharmaceuticals, By Louis D Quin and John A Tyrell Copyright  2010 John Wiley & Sons, Inc THE SCOPE OF THE FIELD OF HETEROCYCLIC. .. the work of Archibald Couper of Scotland, Friedrich Kekul´e of Germany, and Alexander Butlerow of Russia led to the recognition of the tetrahedral nature of the carbon atom and the devising of